Drinking too much soda could affect adolescent memory, ability to learn

FILE - This Feb. 13, 2014 file photo shows sugary sodas in Sacramento, Calif. Since 2005, carbonated soft drinks have been in decline in the U.S. overall, said John Sicher, editor and publisher of the news and data service Beverage Digest. The overall volume has decreased from 10.2 billion cases to 9.2 billion cases. In terms of individual consumption, there's been a corresponding decline. Much of that consumption decline is due to a migration to other categories, primarily bottled water. Between 1999 and 2010, daily calories from soda consumed by 2- to 5-year-olds decreased on average from 106 to 69, according to the National Health and Nutrition Examination Survey, which is conducted by the National Center for Health Statistics. Rich Pedroncelli/Associated Press

If former New York City mayor Michael Bloomberg had waited just a bit longer to wage his public health battle against soda drinks, he could have had more ammunition.

Bloomberg had cited the well-known risks of obesity and diabetes that are associated with excess consumption of sugary drinks when he tried to ban oversized soda pop from being sold at some venues in the city. 

But new research indicates drinking too much soda could also negatively affect the brain, especially for teenagers.

Researchers at the University of Southern California found that drinking beverages sweetened with high-fructose corn syrup or sucrose (that is, soda) every day can impair the ability to learn and remember information.

The research will be presented at the annual meeting of the Society for the Study of Ingestive Behavior in Seattle this week. 

"It's no secret that refined carbohydrates, particularly when consumed in soft drinks and other beverages, can lead to metabolic disturbances," said Dr. Scott Kanoski, the lead author of the study, in a release.

"However, our findings reveal that consuming sugar-sweetened drinks is also interfering with our brain's ability to function normally and remember critical information about our environment, at least when consumed in excess before adulthood."

The researchers gave adult and adolescent rats daily access to sweetened beverages that matched the sugar content found in common soda drinks for 30 days.

Spatial learning trouble

At the end of the month, the researchers tested the rats on their cognitive functions using mazes.

They noticed that the adolescent rats had trouble with their spatial learning, which has to do with navigating the surrounding environment. The drinks also led to a glucose intolerance.

Adult rats, on the other hand, performed the tests normally.

Researchers discovered that when the teen rats drank those sugary beverages every day, it led to inflammation of the hippocampus part of their brains. The hippocampus controls memory and spatial sense. The inflammation is seen to be the reason behind the rats' learning impairment, according to the researchers.

"In many ways this region is a canary in the coal mine, as it is particularly sensitive to insult by various environmental factors, including eating foods that are high in saturated fat and processed sugar," said Kanoski.